This invention relates to an improved method of incorporating carbon fibers into an aqueous hardenable hydraulic cementitious matrix to produce a formable composition which can be set to produce a carbon fiber-reinforced cementitious product having improved flexural strength and improved resistance to cracking and spalling. More particularly, this invention relates to the preparation of a carbon fiber-reinforced structure having improved flexural strength and improved resistance to cracking and spalling from a formable composition containing a polyethylene oxide as a deflocculent to effect uniform dispension of carbon fibers into a hydraulic cementitious matrix.
The use of polyethylene oxide to facilitate the incoporation of fibers into cementitious compositions has been disclosed in U.S. Pat. No. 3,716,386. Thus, according to said patent, small amounts of this material can be employed to prevent clumping of fibrous substances employed in the reinforcement of cement. It has been found, however, that when polyethylene oxide is employed in carbon fiber-reinforced cement in the amounts disclosed in said patent, a decrease in the flexural strength of the product occurs.